The Silent Answer Test (SAT) is the biggest crock of horses**t that was ever devised.
When you are asked to answer sliently in your head, simply screw with his and answer
all questions silently with "Up yours buddy"
Better yet, tell the examiner you would like silent questions and you'll answer out loud.
Smoke and Mirrors my friend.

The "Silent Answer Test" is briefly addressed at p. 157 of the 4th edition of The Lie Behind the Lie Detector. For additional information, see the first post in the discussion thread, Counter-countermeasure Techniques.

Ok have now done, thanks, that is a great book. I am still curious about the silent test however.

Please read Chapters 3 & 4 of The Lie Behind the Lie Detector. These chapters cover polygraph procedure and countermeasures in depth, and should answer most of your questions.

I am going to have to take a polygraph test in a couple weeks and I have a lot of questions, however right now these are my most pressing ones.

With the silent one, forgive my ignorance but couldn't you just not answer the question in your head and think about somethnig else? or couldn't you just answer it correctly in your head and it would show you are telling the truth? The examiner doesn't know what is going on in your head. 

I have heard it said that countermeasures work and I believe it. How easy are they though? I have never in my life taken a polygraph Do they have the ability to prove you are using countermeasures? 

What does tongue biting do? Would the examiner not be able to tell you are tongue biting when you verbally answer the questions?

How do you tell a relevent question from a control question? I would assume they try to make them quite similar. Would a person not get high anxiety from the stress of trying to tell questions apart?